In accordance with the rapid advance in high density and thin film of electronic devices, the problem of influence as to heat generated from IC parts, power parts and high brightness LED becomes serious. In response to this problem, a thermally conductive resin molded article is utilized as a member that conducts heat efficiently between an exothermic body and a heat releasing body.
As a means for endowing the resin with a high thermal conductivity, there has been known that a thermally conductive filler is oriented and dispersed in the resin in order to form a thermal conductive pass efficiently. Further, there has been proposed a thermally conductive resin sheet that is inserted, in order to enhance heat releasing effect, between the electronic part and a heat releasing plate to make the thermal conductivity therebetween better and to improve the thermal conductivity in the thickness direction.
For example, in Patent Literature 1 (Japanese Patent Laid-Open Application H05-102355), there is disclosed an anisotropic thermally conductive sheet where a thermally conductive filler which is surface-treated by coating with a coupling agent is included in a matrix component, and the thermally conductive filler is oriented and dispersed in the thickness direction.
In the anisotropic thermally conductive sheet described in Patent Literature 1, it is possible to obtain an anisotropic thermally conductive sheet which is excellent in thermal conductivity and flexibility under a lower applied voltage than conventional use since an insulation film of the matrix component bonded to the coupling agent is formed on the surface of the thermally conductive filler, when applying a direct current so as to orient the thermally conductive filler in the production step of the anisotropic thermally conductive sheet, there is no ignition due to short-circuit of the thermally conductive filler.
Further, for example, in Patent Literature 2 (Japanese Patent Laid-Open Application 2003-174127), there is disclosed an anisotropic thermally conductive sheet where a surface of a thermally conductive fiber is coated with an electric insulating material, and the thermally conductive fiber is oriented in the thickness direction of the sheet made of an organic polymer by electrostatically flocking.
In the anisotropic thermally conductive sheet described in Patent Literature 2, since the thermally conductive fiber can be oriented in the thickness direction of the sheet, it is possible to obtain an anisotropic thermally conductive sheet which is excellent in thermal conductivity in the thickness direction, and the thickness of the thermally conductive sheet can be adjusted by the length of the fiber.